<template>
  <div>
    <div class="father">
      <div class="box" :class="{ active:id===1}" @click='btn(1)'></div>
      <div class="box" :class="{ active:id===2}" @click='btn(2)'></div>
      <div class="box" :class="{ active:id===3}" @click='btn(3)'></div>
    </div>
  </div>
</template>

<script>
export default {
  data() {
    return {
      id: 1,
    }
  },

  methods: {
    btn(a) {
      this.id = a
    },
  },
}
</script>

<style scoped>
.box {
  border: 1px solid #333;
  width: 250px;
  height: 250px;
}
.father {
  display: flex;
}
.active {
  background-color: #087;
}
</style>
